Typically, a glass substrate of a thin film transistor -liquid crystal display (TFT-LCD) is transferred by a robot in an automated production line of an LCD manufacturing facility. This transfer method is simple and easy to control, but the transmission error is large, especially in fast delivery or long-distance transmission. In an existing production line, the glass substrate is required to be positioned accurately in a machine for special processes, so as to process the glass substrate accurately. However, it is expensive to set a positioning mechanism on the machine, due to complexity of the structure and electronic systems of the machine. Therefore, it brings increase of production cost to set the positioning mechanism on the machine. Furthermore, the positioning effect of the positioning mechanism for the glass substrate is not entirely wishful, which results of reduction of production yield of the TFT-LCD.